Humidity cabinet



5 Sheets -Sheet 1 Filed April 20, 1959 C,IB

/nven/0r W63 49 9 March 2, 1965 J. A. LAWLER 3,171,473

HUMIDITY CABINET Filed April 20, 1959 5 Sheets-Sheet 2 March 1965 J. A.LAWLER 3,171,473

' HUMIDITY CABINET Filed April 20, 1959 lnvenfor f a. M Z

5 Sheets-Sheet 3 March 2, 1965 J. A. LAWLER 3,171,473

HUMIDITY CABINET Filed April 20, 1959 5 Sheets-Sheet 4 M lgenior g .A

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March 1965 A. LAWLER 3, 7 73 HUMIDITY CABINET Filed April 2G, 1959 5Sheets-Sheet 5 sun I comngg om'r BULB 4 c HEATERS u as g so an U v BULBcom United States Patent 3,171,473 HUMIDITY CABENET Joseph A. Lawler,Chicago Heights, Ill assignor to Blue M Electric Company, Blue Island,Ill., a corporation of Illinois Filed Apr. 20, 1959, Ser. No. 807,715 17Elaims. (Cl. 1165-21) This application is a continuation-in-part ofSerial No. 590,951, filed June 12, 1956, and now abandoned.

The invention relates generally to an improved apparatus for controllinga condition of air in a confined chamber and particularly to amechanical convection, controlled humidity device.

It is well known in the art that there is a need for a type of equipmentthat will allow the user to test products under a varying range oftemperature and humidity conditions that the manufactured product may besubjected to in actual use. Particularly, it is necessary for manylaboratories and manufacturers and the like to have equipment of thisnature that will assure them accurate and reliable test results. Withthis in mind, it may be well to briefly consider certain prior artefforts to provide controlled temperature and humidity conditions. Onefrequently used method involves the disposition of chemicals or chemicalsolutions in a confined chamber such as a desiccator jar. Experience hasshown that this method is unsatisfactory for many reasons, among thembeing its high degree of inaccuracy and difficulty of use with theresult that only experienced personnel can utilize it with any degree ofaccuracy. Mechanical devices for controlling temperature and humidity inconfined spaces have also been manufactured, but here again experiencehas shown many disadvantages. In the first instance the designs on themarket today are extremely expensive, and have been found to be bulkyand difficult to work with. Further, these devices have generally nothad the flexibility to afford rapid change in controlled conditions,hence have been unsatisfactory in many use applications. Theseundesirable features have placed these prior art devices outside thepractical scope of most users.

Accordingly, it is a primary object of the invention to provide animproved mechanical convection, controlled temperature and humiditydevice.

Particularly, it is an object of the invention to provide an automatic,economical and conveniently operable mechanism of the type underconsideration offering accurate controlled temperature and humidityconditions, and designed to accommodate rapid and accurate change ofcontrolled conditions. Another feature of the invention is ease ofoperation.

Other objects and advantages of the disclosed arrangement will appear inthe course of the following description and from an examination of theattached drawings, where- 1n:

FIGURE 1 is a perspective View of an embodiment of the invention,

FIGURE 2 is a top plan View of the structure shown in FIGURE 1,

FIGURE 3 is a sectional view, partially in elevation, taken along line33 of FIGURE 2,

FIGURE 4 is a sectional view, partially in elevation, taken along 4-4 ofFIGURE 3,

FIGURE 5 is a schematic of the electrical arrangement employed in theinvention, and

FIGURE 6 is a schematic view of a portion of the control circuitemployed in the arrangement.

Describing the invention in detail, and directing attention to FIGURE 1,it will be seen that the humidity arrangement may comprise a basecabinet 2, which preferably is a rust-resistant metal cabinet of anydesired configuration. The cabinet 2 is provided with an upper 3,171,473Fatented Mar. 2, 1965 horizontal wall 4, upon which rests a transparentjar 6. In the preferred embodiment and for reasons of economy andefficient operation, the jar 6 may be made of transparent,heat-resisting material, and is of cylindrical form. This avoids themanufacture of a chamber having heavily insulated walls and ofrust-resistant material, and additionally provides for convenient visualinspection of work pieces during tests and enables photographs thereofto be taken from many positions. The open end of the jar 6 facesdownwardly and rests upon the upper surface of the wall 4. The jar 6 isdemountable which again provides convenient accessibility to the workchamber and any specimens therein.

The cabinet 2 is provided with a control panel 3 on the front thereofhaving knobs, switches and warning lights which control and visuallyindicate the operation of the arrangement, as will hereinafter be moreparticularly described. One side of the cabinet 2 includes an upwardlyfacing, open-ended housing 10, said housing 10 receiving a jar 12 or thelike which provides a reservoir of liquid such as water, the use ofwhich will also hereinafter be more fully described.

The glass jar a may enclose a plurality of upstanding supporting members14, 14 which connect to Wall 4, said members 14 supporting a shelf Inwhich may hold work pieces during operation of the arrangement. ineffect, the jar 6 defines with the wall 4 a workpiece chamber 13internally thereof. A radially inwardly directed arm 2t) may be securedto an upper end of one of the members 14 and may carry centrally of thechamber 1% and adjacent the top of jar s, a drip plate 22 which willcatch any condensed liquid that may collect on the top of the jar andprevent same from falling on the work pieces in the chamber 18. FIGURE2, a top plan view of the structure shown in FIGURE 1, clearlyillustrates the physical relation of the parts of the structuredescribed.

Directing attention to FIGURE 3, it will be seen that the cabinet 2 hasprovided therein a conditioning chamber 2 said conditioning chamberbeing located immediately below the wall 4. A central aperture orpassage 26 is provided in the wall 4 and establishes communicationbetween the workpiece chamber 18 and the conditioning chamber 24. Apivoted damper plate 27 may be provided to selectively vary the area ofthe passage 26 or even to complete closure, the use of which will belater explained in detail. The chamber 24 is arranged to contain asubstantially static liquid pool 28, usually water, at the bottomthereof and having a surface 30 generally coextensive with the area ofthe conditioning chamber 24. The jar 12, disposed in said housing 10, ispositioned with its open mouth facing downwardly and supported in spacedrelation to the bottom of the housing whereby the liquid therein isallowed to escape into the housing and is carried via pipe 32, whichcommunicates with chamber 24, so as to maintain a substantially constantlevel of liquid in the conditioning chamber 24 to replenish anyevaporation therefrom which may escape from the system.

An operator motor 34 may be positioned in the bottom of the cabinet 2 inany suitable manner, such as by mounting to a supporting bracket 36. Themotor 34 has its rotatable operating shaft 38 extending upwardly througha liquid-tight aperture 49 in the bottom of the conditioning chamber24-. A centrifugal blower 42 is fixedly secured to shaft 38, and ispositioned immediately below the aperture 26 in the wall 4. When themotor 34 is operating, as hereinafter described, air will be moved fromworkpiece chamber 18 through the passage 26 by the blower 42 and thendischarged generally outwardly therefrom.

Cooling means may be provided in operative heat ex- C9 changerelationship with the air circulated by the blower 42, and in thepreferred embodiment the cooling means comprises a helically Wound coil44 of good conductive material which surrounds the blower 42 radiallyoutwardly therefrom. A first bafile or plate 46 is secured to theunderside of the wall 4 and is located outwardly of the coil 44'and inradially spaced surrounding relation thereto.

A second annular baflle or plate 48 is provided in the conditioningchamber 24 and adjacent the outer edge thereof, said battle 4%.extending from the wall 4 downwardly to substantially the bottom of thechamber, and in such position that it forms an inverted cone surroundingthe previous described structure. It will be noted that the battle 43presents an inner surface that is directed upwardly toward a pluralityof peripherally disposed apertures or passages t), it? which areannularly arranged in the wall 4, and preferably about the periphery ofchamber lb. As will readily be observed, any moisture condensing in theworkpiece chamber 18 will drain back to the liquid pool 28 through thepassages 50. A plurality of mounting clips 52, 52 may be secured to theinner surface of the battle 48 and provide a convenient means formounting electrical heating elements 54 which are annularly arrangedaround the conditioning chamber 24 and immediately below the passages50. The heating elements 54 constitute the dry bulb heater illustratedin the schematic of FIGURE 5, later to be described. Additionally, aheating element 56 may be disposed in the liquid 28, said heatingelement 56 constituting the wet bulb heater illustrated in FIG- URE 5. 7

An additional physical feature of the arrangement is a passage or tube58 which is provided in the cabinet 2; and extends upwardly through thewall 4 should the user desire to connect the test specimens to anexternal recording device (not shown). An electrical conduit as issimilarly provided in the cabinet 2 and extends into the workpiecechamber 18 and offers a plurality of electrical connections whichcommunicate with a connection bar 62 externally of the cabinet toprovide convenient electrical connection to any workpiece in the chamber18 should it be desired to operate the specimens during test.

Directing attention to FIGURES 5 and 6, wherein are schematicallyillustrated the controlling heating and cooling circuits employed in theinvention, it will be seen that a main switch 68 is provided, said mainswitch connecting the electrical circuit, indicated generally at 7@, toa conventional power source which may be a standard 120-volt A.C. line.A warning light L-ll is provided across the switch 68 to visuallyindicate that the arrangement is turned on. Closure of switch 68immediately energizes the motor 34 which, of course, induces rotation ofthe blower 42, and circulation of air from the workpiece chamber 18through the passage 26, through conditioning chamber 24 and upwardlythrough apertures 5t). Another important point in connection with theperipheral location of apertures 50 is that during air circulation, theair passing through apertures 5h will flow upwardly to the top of, thechamber 18 before recirculating through the passage 26. This assurescomplete air circulation through the'chamber 18 and results in constantcontrolled conditions throughout its entire volume.

A dry bulb controlling circuit 72 is provided in the circuit '70, saiddry bulb controlling circuit being arranged to operate the dry bulbheaters 54. The dry bulb control 74 comprises a temperature-sensitiveelement 76 positioned in the workpiece chamber 18, and preferablyadjacent the apertures 5h. The element 76 senses the temperature in thechamber 13 and control '74 thermostatically responds theretoin aconventional manner to control the application of power to circuit 72,and hence is not structurally described in detail. A power selectorswitch 78 is also provided in the circuit 72, said switch 78 being aconventional type switch to selectively pro- .vide energizing power inthree stages to the heating elements 5i-that is, upon proper settingthereof the elements 54- may be connected individually, in series or inparallel to provide varying levels of available heat application, thepurpose of which will hereinafter be described. A pilot light L-2 isarranged in parallel with the dry bulb heaters 54 to visually notify theoperator when the dry bulb heaters are energized.

A web bulb control circuit St) is also provided in the circuit 70, saidwet bulb circuit controlling the relay 82 which in turn controls theposition ofa two-position switch The wet bulb control 86 comprises atemperaturesensitive element 88 which is located in the conditioningcompartment 24 and preferablyin abutting relationship with a portion ofthe cooling coil 44, as is shown in FIG- URES 3 and 4. One fixed contact90 of the switch 84 is in series relation with the wet'bulb heat element56. Again, a pilot light L-3 is in parallel with the wet bulb heater 55to visually advise the operator when the wet bulb heater is energized.The other fixed contact 94 of the two-position switch 34 is in serieswith a solenoid valve which, in turn, controls the application ofcooling medium to the cooling coil 44. Again, a pilot light L-d isarranged in parallel with the solenoid as to visually advise theoperator when the solenoid is energized, and therefore when coolingmedium is flowing.

FIGURE 6 illustrates the piping arrangement to the cooling coil 44, andit will be seen that a line 1% may be connected to a cooling source (notshown). The solenoid valve 96 is in operative series relation in theline lltltl, said line 1% also having a manually openable and closablevalve 102 therein. Another line lii l establishes communication with thecooling coil and a further line 1% communicates with the ot er end ofthe coil 44 to carry the cooling medium to exhaust. A by-pass line 1%communicates with the line ran between the source and the solenoid valve96 and establishes communication with the line 1M through a manuallyoperated by-pass valve 110. The reason for this by-pass arrangement willbe hereinafter explained in detail.

Before considering the operation of the arrangement, those skilled inthe art will understand that the range of temperatures and humiditiesavailable in a cabinet of this nature is functionally responsive to aminimum temperature available by virtue of the cooling medium used inthe coil 44. I have discovered that most tests run by commercial usersof equipment of this nature fall into a relatively high humidity rangeand dry bulb temperature above ambient, and therefore tap water cannormally be used as a coolant. However, if an increased range of bothtemperature and humidity level is desired, they can be made available bymerely substituting for the tap water coolant a refrigerant capable ofproviding lower cooling temperatures.

Directing attention to FIGURE 5, it will be remembered that the powerselector switch '78 can be set at low, medium or high range, dependingon the particular temperature to be maintained, and thus the generalrange of average heat input required, in a particular test run. It willalso be understood that the dry and wet bulb controls may be providedwith dials (not shown) available on the control panel 8, said dialsbeing manually adjustable to a desired temperature calibrated in degreesFahrenheit or centigrade, whereby a given temperature selection may beeasily and quickly located. Gf course, the dry bulb control isresponsive to temperature of the air exiting into the workpiece chamber,and the wet bulb control is responsive to the temperature in theconditioning chamber and to a small extent, for purposes-of minimizingresponse time, to temperature of the coil 4-4 which it physically abutsand touches at one point as shown in the drawing. Independentthermometers may be used in the respective chambers to check theaccuracy of the calibrated dials and make corrections if necessary.

Considering a typical operation of the arrangement, it will beunderstood that by reference to a conventional psychometric chart adetermined dry bulb temperature and relative humidity will then affordthe user the desired wet bulb temperature to produce the givenconditions. The dry bulb and the wet bulb temperature are then properlyset, and the arrangement may be turned on by closing switch 68. Closureof switch 68 immediately energizes the motor 34 which sets up acirculation of air by drawing from the workpiece chamber 18 through thecentral aperture 26 and urging the air outwardly over the cooling coil44 and, with the aid of halide as, over and across the surface 35 of theliquid 28 from whence it is directed upwardly by baffle 43 over theelements 54 and up through the peripheral apertures 50 and into theworkpiece chamber 18. Circulation once started is constant and continuesduring the entire run. The dry bulb control '74 senses the temperaturesin the air exiting into the workpiece chamber 18 and energizes theheating element 54, the level of which is determined by the powerselector switch 78. The elements 54 continue to heat the passing airuntil such time as the temperature reaches the desired level in thechamber 13, whereupon they will deenergize in response to action of thecontrol 74. Intermittent action of the control 74 in response to sensedtemperature variation of the air exiting into the chamber 18 willintermittently energize the elements 54 and will accurately maintain thedry bulb temperature in the chamber 18.

The circuit through the wet bulb heater 56 responds to the action of thewet bulb control 86 which selectively energizes the relay 82. The switch84 normally connects contact 94 which establishes a circuit through thesolenoid valve as which, in turn, accommodates flow of coolant throughthe coil 44. As the temperature of the air coming into the conditioningchamber 24 is lowered to or slightly below a dew point temperturecorresponding 7 to the total volume of water vapor in the air at theselected relative humidity, the wet bulb control 86 energizes the relay82, bringing the switch 84 to the contact 9% which establishes a circuitthrough the wet bulb heater 56 energizing same. This, of course, heatsthe liquid 28 causing an increased rate of evaporation thereof and morerapidly bringing the air in chamber 24 to a saturated condition. Thisaction tends to raise the temperature of the air in chamber 24, and thischange is sensed by the wet bulb control 85 which deneregizes the relay82 and re turns the switch 84 to contact 94-, which again provides forcirculation of coolant through the coil 44 by energizing the solenoidvalve 5%. Thus, the temperature in chamber 24 is accurately maintainedat the approximate desired level. It will be understood that especiallyin the more frequently used high humidity test conditions, the wet bulbcontrol selectively and alternately energizes the solenoid valve and thewet bulb heater to selectively and alternately provide for heating andcooling of the air and selective heating of the liquid in theconditioning chamber 24, as Well as tending to control the rate ofevaporation in said conditioning chamber 24. The abutting juxtapositionof the wet bulb sensing element $8 with the coil 44 provides increasedsensitivity and more rapid response relative to controlling temperatureand humidity condition in the conditioning chamber 24, and thereforeimproves the efficiency of the entire arrangement. I have found thatthis feature tends to produce a somewhat greater and more rapid changein the sensing element than in the acted-on medium itself, which resultsin a finer tolerance control. In effect, medium change is anticipated orrushed in the sense that the conditions may be controlled with a smallercycling range than could be obtained if only air conditions were beingsensed. The value of this operative feature will be appreciated by thosewho have experienced the difficulty of running high humidity testswithout having undesired condensation on test specimens. The accurateand close tolerance control avoids temporary temperature creep duringthe operating cycle which may otherwise resuit in periodic condensationon work specimens.

Considering FIGURE 6, it was earlier noted that a manual by-pass valvewas provided to afford circulation of cooling medium through the coil 44to by-pass the control of the solenoid valve 96. This arrangement isdesirable when the determined operating conditions in the workpiecechamber 18 involve a relatively high humidity at a comparatively low drybulb temperature. Operating under these conditions, the solenoid valve96 is rarely if ever energized, and as a result no coolant will flowthrough coil 44. On the other hand, the wet bulb control will tend toconstantly energize the wet bulb heater with the result that there is atendency to cause a slight climbing or raising in the temperature of thecirculated air, and to prevent this and remove the excess heat producedby the wet bulb heater, it is desirable to open valve 119 and allow aflow of a small quantity of coolant through the coil 44. Thiseffectively removes the excess heat produced and creates a balance ofheat input and cooling effect, which result in the accurate maintenanceof the desired dry bulb temperature in the workpiece chamber 18 underthese extreme conditions.

The pivoted damper plate 27 is available to vary the area of passage 2eand thereby control the rate of air flow through the entire unit. Whenclosed entirely, the air flow is reduced to approximately zero cubicfeet per minute and the entire unit becomes, in essence, a gravityincubator accommodating high humidity resulting in desired con densationon work pieces. As the volume of air flow is varied, the rate ofevaporation of moisture condensed on test work pieces also varies, aseven with high humidity air, the rate of evaporation varies with therapidity and volume with which the surrounding air moves. This featureis of advantage in conducting tests relating to the rate of evaporationof condensed moisture on work pieces and operation thereunder.

Thus, it will be seen that I have provided a novel device of the typehere under consideration that is economical to produce, highly accurateand versatile in operation, and offers advantages and results heretoforenot found in the art. The arrangement particularly is adaptable tosmall, compact, inexpensive units which satisfy the needs of themajority of users of this type of equipment. The device as shown is byway of illustration and not limitation, and may be subject to variousmodifications without departing from the spirit thereof and the scope ofthe appended claims.

I claim:

1. A temperature and humidity conditioning device comprising a chamber,an air inlet and air outlet in horizontally spaced portions of thechamber, a substantially stationary pool of liquid in the bottom of thechamber, an enclosing .top on the chamber in the region between the airinlet and outlet, variable heat-removal cooling means exterior to theliquid in the air flow path adjacent to the air inlet, the pool ofliquid being at least partially in the region of the chamber between thecooling means and the outlet, means to evaporate the liquid into theregion between the liquid and the enclosing top, heating means adjacentto the air outlet, a temperature-sensing element in the portion of thechamber between the cooling means and the air outlet responsiveprimarily to the temperature of the air in said portion, meansresponsive to said temperature-sensing element to increase the heatremoval of the cooling means when the temperautre sensed exceeds apreset value and to reduce the heat removal of the cooling means whenthe temperature sensed falls below a preset value, means for passing airfrom the inlet to the outlet through the chamber, and means adjacent tothe air outlet to control the heating means to maintain the exittemperature constant at a preset value.

2. A temperature and humidity conditioning device comprising a chamber,an air inlet and air outlet in horizontally spaced portions of thechamber, a substantially stationary pool of liquid in the bottom of thechamber, an enclosing top on the chamber in the region between the airinlet and outlet, variable heat-removal cooling means exterior to theliquid in the air fiow path adjacent to the air inlet, the pool ofliquid being at least partially in theregion of the chamber between thecooling means and the outlet, heating means adjacent to the air outlet,second heating means in the liquid to evaporate the liquid into theregion between its surface and the enclosing top, a temperature-sensingelement in the portion of the chamber between the cooling means and theair outlet above the surface of the liquid responsive primarily to thetemperature of the air in said portion, means responsive to saidtemperature-sensing means to increase the heat removal of the coolingmeans and decrease the heat input of the second heating means when thetempenature sensed exceeds a preset value, and to decrease the heatremoval of the coolingmeans and increase the heat input or thesecondheatingmeans when the temperature sensed falls below a presetvalue, means for passing air from the inlet tov the outlet through thechamber, and means adjacent to the air outlet to control the heatingmeans to maintain the exit temperature constant at a preset value.

3. The device of claim 2 wherein the means to increase and decrease theheat removal and heat input comprises a double-throw switch connected toselectively energize the cooling means and the second heating means.

4. A temperature and. humidity conditioning device comprising a chamber,an air inlet and air outlet in horizontally. spaced portionsof thechamber, a substantially stationary pool of liquid inthe bottom of thechamber, an enclosing top on the chamber in the region between the airinlet and outlet, selectively operable cooling means exterior to-theliquid in the air flow path adjacent to the air inlet, the poolof liquidbeing at least partially in the region of the chamber between thecooling means and the outlet, means for evaporating the liquid, heatingmeans adjacent to the air outlet, a temperature-sensing element in theportion of the chamber between the cooling means-and the air outletresponsive primarily to the air temperature in said portion, meansresponsive to said temperature-sensing element to activate the coolingmeans when the temperature sensed exceeds a preset value and toinactivatethe cooling means when the temperature sensed falls below apreset value, means for passing air from the inlet to the outlet throughthe chamber, and means adjacent to the air outlet to control the heatingmeans to maintain the exit temperature constant at a preset value.

5. A humidity cabinet comprising a conditioning chamher, a workpiecechamber atop the conditioning chamber, a central air passage and aplurality of symmetrically dis tributed peripheral air passagesconnecting the chambers, a body of liquid in the bottom of theconditioning chamber, means for circulating air into the conditioningchamber through the central passage, radially over the surface of theliquid, and out through the peripheral passages,

selectively operable cooling means exterior to the liquid in theconditioning chamber closely surrounding the central passage, heatingmeans adjacent to the peripheral apertures, a temperature-sensingelement in the portion of the conditioning chamber outwardly adjacent tothe cooling means responsive primarily to the temperature of the air insaid portion, means responsive to said temperature-sensing element toactivate the cooling means when the temperature sensed exceeds a presetvalue and inactivate the cooling means when the temperature sensed fallsbelow a preset value, means to evaporate the liquid, and means adjacentto the peripheral passages to control the heating means to maintain theexit temperature constant at a preset value.

6. A. temperature and humidity conditioning device comprising aconditioning chamber, a central air passage and a plurality ofsymmetrically distributed peripheral air passages in the top of thechamber, a body of liquid in the bottom of the chamber, means forcirculating air into the conditioning chamber through the centralpassage, radially over the surface of the liquid, and out through theperipheral passages, selectively operable cooling means exterior to theliquid in the conditioning chamber closely surrounding the centralpassage, heating means adjacent to the peripheral apertures, atemperature-sensing element in the portion of the conditioning chamberoutwardly adjacent to the cooling means responsive primarily to thetemperature of the air in that portion, means responsive to saidtemperature-sensing element to activate the cooling means when thetempenature sensed exceeds a preset value and inactivate the coolingmeans when the temperature sensed falls below a preset value, means toevaporate the liquid, and means adjacent to the peripheral passages tocontrol the heating means to maintain the exit temperature constant at apreset value.

7. A temperature and humidity conditioning device comprising a chamber,a central air passage and a plurality of symmetrically distributedperipheral air passages in the top of the chamber, a body of liquid inthe bottom of the chamber, a blower adjacent to the central passagedisposed to draw air therethrough into the chamber and distribute itradially over the surface of the liquid and out through the peripheralpassages, a cooling coil surrounding the blower and having a valvecontrolling the flow of cooling fluid therethrough, first heating meansadjacent to the peripheral apertures, second heating means in theliquid, a temperature-sensing element in the portion of the chamberoutwardly adjacent to the cooling coil primarily responsive to thetemperature of the air in said portion, means responsive to saidtemperature-sensing element to inactivate the second heating means andopen the valve when the temperature sensed exceeds a preset value and toactivate the second heating means and close the valve when thetemperature sensed falls below a preset value, and means adjacent to theperipheral passages to control the first heating means to maintain theexit temperature constant at a preset value.

8. A humidity cabinet comprising a conditioning chamber, a workpiecechamber atop the conditioning chamber, a central air passage and aplurality of symmetrically distributed peripheral air passagesconnecting the chambers, a body of liquid in the bottom of theconditioning-chamber, a blower adjacent to the central passage disposedto draw air therethrough into the conditioning chamber and distribute itradially over the surface of the liquid and out through the peripheralpassages, a cooling coil surrounding the blower and having a valvecontrolling the flow of cooling fluid therethrough, first heating meansadjacent to the peripheral apertures, second heating means in theliquid, a temperature-sensing element in the portion of the conditioningchamber outwardly adjacent to the cooling coil responsive primarily tothe temperature of the air in that portion, means responsive to saidtemperature-sensing element to inactivate the second heating means andopen the valve when the temperature sensed exceeds a preset value and toactivate the second heating means and close the valve when thetemperature sensed falls below a preset value, and means adjacent to theperipheral passages to control the first heating means to maintain theexit temperature constant at a preset value.

9. The conditioning device of claim 8 wherein the temperature-sensingelement includes temperature-sensing means partially responsive to thetemperature of the coil.

10. A temperature and humidity conditioning device comprising a chamber,an air inlet and air outlet in horizontally spaced portions of thechamber, means for impelling air from the inlet to the outlet, coolingmeans in the air flow path adjacent to the air inlet portion, adjustablyvariable temperature control means primarily responsive to airtemperature in the region between the cooling means and the air outletportion to hold said last temperature constant, means including asubstantially stationary pool of water on the bottom of the chamber insaid region for saturating the air in said region with moisture, andadjustably variable controlled heating means to heat the outlet air tofixed temperatures, whereby the inlet air is cooled, saturated withvapor at the selected constant temperature fixed by the control means,heated to a selected constant temperature fixed by the controlledheating means, and emitted at the temperature and humidity thus fixed,substantially independently of the conditions of the inlet air.

11. A temperature and humidity cabinet comprising a work space, aconditioning chamber below the work space, means for circulating airfrom the work space into an inlet portion of the conditioning chamber,through the conditioning chamber, and out of an outlet portion of theconditioning chamber horizontally spaced from the inlet portion andincluding openings connecting the work space and chamber, means in theinlet portion of the conditioning chamber to cool the air, manuallyvariable means in the region between the inlet portion and outletportion responsive to air temperature in this region to maintain suchtemperature at preselected values and to saturate the air at suchconstant temperature, the saturating means including a body of liquid onthe bottom of the chamber, so that moisture condensed in the work spacedrains back to the body of liquid through the openings, and manuallyvariable means to heat the air to preselected constant temperature inthe outlet portion.

12. A temperature and humidity cabinet comprising a conditioning chamberhaving a substantially horizontal top, a central aperture in the top ofthe conditioning chamber, apertures in the top of the conditioningchamber dispersed in a circle about said central aperture, a circularenclosure defining a Work space atop the conditioning chambersurrounding the circularly dispersed apertures, the apertures beingadjacent to the periphery of the work space and the central andperipheral apertures defining the sole air passages between theconditioning chamber and the Work space, radially extending circularconditioning means in the chamber including means to control thetemperature and humidity of air passing radially through the chamber,and a blower on the axis of the chamber adapted to circulate airradially through the conditioning 10 chamber, whereby differences in airconditions in the work space are minimized.

13. The cabinet of claim 12 wherein the enclosure comprises a unitarycup-shaped inverted member, whereby the simple enclosure thus formed maybe completely removed to give full access to the work space from anydirection.

14. A temperature and humidity cabinet comprising the conditioningdevice of claim 10 having thereabove an enclosure defining a work space,the air inlet and air outlet being in the top of the chamber anddefining the sole air paths between the chamber and the work space.

15. The temperature and humidity cabinet of claim 14 wherein one of saidair paths is central of the enclosure and the other is substantiallyuniformly distributed about the bottom of the work space adjacent to theperiphery thereof.

16. The temperature and humidity cabinet of claim 15 wherein theenclosure is circular.

17. The temperature and humidity cabinet of claim 16 wherein theenclosure is a unitary inverted cup-shaped member.

References Cited in the file of this patent UNITED STATES PATENTS1,821,886 Fleisher Sept. 1, 1931 1,919,197 Bulkeley July 25, 19331,971,405 Harris Aug. 28, 1934 2,093,691 Buder Sept. 21, 1937 2,093,968Kettering Sept. 21, 1937 2,137,996 Crawford Nov. 22, 1938 2,219,861Anderson Oct. 29, 1940 2,244,551 Crawford June 3, 1941 2,266,238 NewtonDec. 16, 1941 2,286,551 Kingsland June 16, 1942 2,287,997 Jarvis June30, 1942 2,482,753 Heineman Sept. 27, 1949 2,545,491 Ohlheiser Mar. 20,1951 2,546,417 Anglin Mar. 27, 1951 2,608,831 Steehnan Sept. 19, 19522,667,336 Lethane et al Jan. 26, 1954 2,763,135 Holderle et a1 Sept. 18,'1956 2,915,884 Haushatter et a1 Dec. 8, 1959

1. A TEMPERATURE AND HUMIDITY CONDITIONING DEVICE COMPRISING A CHAMBER,AN AIR INLET AND AIR OUTLET IN HORIZONTALLY SPACED PORTIONS OF THECHAMBER, A SUBSTANTIALLY STATIONARY POOL OF LIQUID IN THE BOTTOM OF THECHAMBER, AN ENCLOSING TOP ON THE CHAMBER IN THE REGION BETWEEN THE AIRINLET ON OUTLET, VARIABLE HEAT-REMOVAL COOLING MEANS EXTERIOR TO THELIQUID IN THE AIR FLOW PATH ADJACENT TO THE AIR INLET, THE POOL OFLIQUID BEING AT LEAST PARTIALLY IN THE REGION OF THE CHAMBER BETWEEN THECOOLING MEANS AND THE OUTLET, MEANS TO EVAPORATE THE LIQUID INTO THEREGION BETWEEN THE LIQUID AND THE ENCLOSING TOP, HEATING MEANS ADJACENTTO THE AIR OUTLET, A TEMPERATURE-SENSING ELEMENT IN THE PORTION OF THECHAMBER BETWEEN THE COOLING MEANS AND THE AIR OUTLET RESPONSIVEPRIMARILY TO THE TEMPERATURE OF THE AIR IN SAID PORTION, MEANSRESPONSIVE TO SAID